The present invention relates to measurement of object configurations and more particularly concerns determination of three dimensional configurations. Methods and apparatus of the invention may be employed to obtain different profiles of the same object to facilitate definition of three dimensional configuration of the object.
Inspection of configuration of manufactured parts is frequently necessary and always desirable, yet difficult, expensive and time consuming. Commonly, such configuration inspection requires direct measurement of different elements and features of the manufactured article. In the maufacture of bent tube, such as automobile exhaust pipe for example, in which a number of straight portions are connected by several bends, it is necessary to measure in three dimensions the axes of the several straight portions in order to define the length of the straight portions, the angle of the bend between adjacent straights and the angle of the plane of one bend with respect to the plane of another bend. Commonly, such measurements are made by a probe mounted for translation or motion along three coordinate axes as, for example in the machines shown in U.S. Pat. Nos. 3,774,311 to Stemple and 3,774,312 to Sesch. These machines are of limited application because the size of the machine itself determines the size of the object that may be measured. Costs increase rapidly with increasing size. In such machines it is exceedingly difficult to maintain precision of position and motion of traveling cantilevered elements. In addition to these and other problems, such machines require time consuming physical manipulation to make contact with the object being measured at a number of different points. Such manipulations require a skilled or at least a trained and experienced operator.
A significant improvement in such three dimensional measuring devices is described in my prior U.S. patent for Method and Apparatus for Measuring Direction, U.S. Pat. No. 3,944,798, in which a five axis articulated probe has a working head that may be oriented in three dimensions so as to align itself with any straight portion of the tube. This arrangement permits measurement of the vector that is parallel to a tube axis to be made with but a single operation. Nevertheless, even with this improved instrumentation the object being measured, whether a tube or some other object with a three dimensional configuration that is to be determined and inspected, must be clamped to a support and then contacted with the measuring instrument at least once for each straight portion in order to obtain the desired information. This operation is time consuming and may cause undesired delay, particularly in quantity production or where many parts must be carefully inspected as rapidly as possible.
Optical scanning devices for making a single measurement such as a width or thickness, are well known. Examples of such devices are shown in the U.S. Pat. No. 3,533,701 to Hruby et al and in U.S. Pat. No. 3,615,139 to Bostrom. In these patents a light beam is moved across an object to be measured and the time of occlusion of the light beam by the object is employed as a measure of the distance across the object. These devices are useful for measurement of but a single dimension and cannot obtain any three dimensional configuration measure. The scanning beam moves only in a single direction relative to the object being measured.
The U.S. patent to Danielson et al U.S. Pat. No. 2,954,266, employs an arrangement for measuring the pitch of a helix in which a helical object is moved past a light source and a pair of relatively movable optical gratings are employed for inspection of pitch uniformity of a traveling wave tube helix. Only a single measurement along a single axis is made. No three dimensional measurement or inspection is possible.
Accordingly, it is an object of the present invention to provide methods and apparatus for inspection and measurement of configuration which avoid or minimize above-described problems and limitations of prior art devices.